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Team Sports

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Team Sports
Chapter 44
Team Sports
JENS BANGSBO
Introduction
In determining proper nutritional recommendations in a sport discipline, it is important to assess
the requirements of the sport and determine
whether substrate availability may limit performance. In team sports such as basketball, rugby,
soccer, hockey, ice-hockey, volleyball and team
handball, the players perform many different
types of exercise. The intensity can alter at any
time and range from standing still to sprinting
(Fig. 44.1). This is in contrast to sports disciplines
such as a 100-m sprint and a marathon run, in
which during the entire event continuous exercise is performed at a very high or at a moderate
intensity, respectively. Due to the intermittent
nature of team sports, performance may not only
be impaired toward the end of a match, but also
after periods of intense exercise. Both types
of fatigue might be related to the metabolic
processes that occur during match-play. Therefore, before discussing the diet of athletes in team
sports, energy provision and substrate utilization during intermittent exercise and in team
sports will be considered.
Energy production and substrate
utilization in team sports
In most team sports, the exercise performed is
intermittent. It is therefore important to know
how metabolism and performance during an
exercise bout are influenced by previous exercise.
Through the years, this has been investigated
574
systematically by changing one of the variables
at a time. Such studies form the basis for understanding the physiology of intermittent exercise.
It has to be recognized, however, that in most laboratory studies the variations in exercise intensity and duration are regular, whereas in many
intermittent sports the changes in exercise intensity are irregular and can be almost random.
Anaerobic energy production
In one study, subjects performed intermittent
cycle exercise for 1 h, alternating 15 s rest and 15 s
of exercise at a work rate that for continuous
cycling demanded maximum oxygen uptake
(Essen et al. 1977). Considerable fluctuations in
muscle levels of adenosine triphosphate (ATP)
and phosphocreatine (PCr) occurred. The PCr
concentration after an exercise period was 40% of
the resting level, and it increased to about 70% of
the initial level in the subsequent 15-s recovery
period, whereas the increase in muscle lactate
was low.
Also during competition in team sports, the
PCr concentration probably alternates continuously as a result of the intermittent nature of the
game. Figure 44.2 shows an example of the fluctuations of PCr determined by nuclear magnetic
resonance (NMR) during three 2-min intermittent exercise periods that each included short
maximal contractions, low-intensity contractions
and rest. A pronounced decrease of PCr was
observed during the maximal contractions, but it
almost reached pre-exercise value at the end of
team sports
575
100%
100-m
sprint
.
VO2 max
Marathon
Basketball
20
each 2-min intermittent contraction period (Fig.
44.2). Thus, although the net utilization of PCr is
quantitatively small during competition in team
sports, PCr has a very important function as an
energy buffer, providing phosphate for the
resynthesis of ATP reaction during rapid elevations in the exercise intensity, and the availability
of PCr may determine performance during some
intense periods of a game.
Lactate in the blood taken during match-play
may reflect, but underestimate, the lactate production in a short period prior to the sampling.
Thus, the concentration of lactate in the blood
is often used as an indicator of the anaerobic
lactacid energy production in sports. In several
team sports like basketball and soccer, high
lactate concentrations are often found, suggesting that lactate production during a match can be
very high.
60
80
Time (s)
100
120
140
160
100
90
80
70
60
50
40
(a)
0
1
0
1
2
3
4
5
6
2
3
4
5
6
100
80
60
40
20
0
Aerobic energy production
Heart rate determinations during match-play
can give an indication of the extent to which the
aerobic energy system is taxed. In many team
sports, such as basketball, team handball and
soccer, the aerobic energy production is high. For
example, it has been estimated that the mean
relative work rate in soccer is around 70% of
maximum oxygen uptake, although the players
are standing or walking for more than one third
of the game (Bangsbo 1994a). One explanation of
Ice hockey
40
Phosphocreatine (% of rest)
0
Work load (% of MVC)
Fig. 44.1 Examples of pattern of
exercise intensities in various
sports.
(b)
Time (min)
Fig. 44.2 (a) Phosphocreatine concentration in the
gastrocnemius muscle determined by NMR during
isometric contractions with the calf muscles at
alternating work loads (b). The exercise consisted of
three identical 2-min contraction periods, each
including a maximal contraction. MVC, maximum
voluntary force of contraction. Adapted from Bangsbo
(1994a), with permission from Acta Physiologica
Scandinavica.
576
sport-specific nutrition
the high aerobic energy utilization is that oxygen
uptake in the recovery periods after intense exercise is high (Bangsbo 1994a).
Substrate utilization
The large aerobic energy production and the pronounced anaerobic energy turnover during
periods of a match in many team sports are associated with a large consumption of substrates.
The dominant substrates are carbohydrate and
fat, either stored within the exercising muscle or
delivered via the blood to the muscles.
The carbohydrate used during a match is
mainly the glycogen stored within the exercising
muscles, but glucose extracted from the blood
may also be utilized by the muscles. Information
about the use of muscle glycogen during a match
can be obtained from determinations of glycogen
in muscle samples taken before and after the
match. The difference in glycogen content represents the net utilization of muscle glycogen, but it
does not show the total glycogen turnover, since
some resynthesis of glycogen probably occurs
during the rest and low-intensity exercise
periods during a match (Nordheim & Vøllestad
1990; Bangsbo 1994a). Muscle glycogen utilization may be high in team sports. As an example,
in a study of Swedish soccer players the average
thigh muscle glycogen concentrations of five
players were 96, 32 and 9 mmol · kg–1 wet weight
before, at half-time and after a non-competitive
match, respectively (Saltin 1973). An important
aspect to consider in intermittent sport is that
even though the muscle glycogen stores are not
completely depleted, the level of muscle glycogen may be limiting for performance (see below).
Fat oxidation is probably high during most
team sports. Studies focusing on recovery from
intense exercise and intermittent exercise
suggest that fat is oxidized to a large extent after
intense exercise (Essen 1978; Bangsbo et al. 1991).
The primary source of the fat oxidized in the rest
periods in between the more intense exercise
may be muscle triacylglycerol (Bangsbo et al.
1991).
The role of protein in metabolism in team
sports is unclear, but studies with continuous
exercise at a mean work rate and duration similar
to team sports such as soccer and basketball have
shown that oxidation of proteins may contribute
less than 10% of the total energy production
(Wagenmakers et al. 1990).
As an example, an estimation of substrate utilization and energy production during a soccer
game is shown in Fig. 44.3. It is clear that muscle
ATP + PCr
100
300
Anaerobic
98
200
50
0
80
Aerobic
150
100
96
Muscle
glycogen
Blood
glucose
Fat
Protein
60
40
20
0
Energy turnover (%)
Substrate utilization (g)
250
Fig. 44.3 Estimated relative
aerobic and anaerobic energy
turnover (right) and
corresponding substrate
utilization (left) during a soccer
match. Adapted from Bangsbo
(1994a), with permission from
Acta Physiologica Scandinavica.
team sports
glycogen is the most important substrate in
soccer and likely also in other team sports.
It should be noted that in team sports large
interindividual differences exist in the energy
production during a match due to the variety of
factors influencing the exercise intensity, e.g.
motivation, physical capacity and tactical limitations. Therefore, there may be major individual
variations in the demand of players in the same
team.
Diet in team sports
In this section the importance of nutrition in
team sports is discussed and dietary recommendations to accommodate nutritional requirements for training and matches are provided. It
should be emphasized that maintaining an adequate diet will improve the potential to reach a
maximum level of performance, but does not
ensure good performance during a match. There
are many other factors that influence performance, including technical abilities and tactical
understanding.
Diet and performance in intermittent exercise
It is well established that performance during
long-term continuous exercise is improved by
intake of a carbohydrate-rich diet in the days
before the exercise. In order to evaluate whether
a diet high in carbohydrate also affects performance during prolonged intermittent exercise,
a study of eight top-class Danish players was
performed.
A soccer-specific intermittent exercise test was
used to evaluate performance (Fig. 44.4). The
players ran intermittently until they were
exhausted and the test result was the total
distance covered. The average exercise intensity during the tests was 70–80% of maximum
oxygen uptake, which resembles the average
intensity during several team sports such as team
handball, soccer and basketball. The players performed the test on two occasions separated by 14
days. On one of the occasions, the test was
carried out with the players having ingested a
577
diet containing 39% carbohydrate (control diet;
C-diet) during the days before the test, and on
the other occasion the players performed the test
having consumed a high (65%) carbohydrate diet
(CHO-diet) prior to the test. Both tests were
carried out 3 days after a competitive soccer
match, with the diets maintained during the 2
days following the match. The order of the tests
was assigned randomly. The total running distance of 17.1 km after the CHO-diet was significantly longer (0.9 km) than after the C-diet. Thus,
increasing the carbohydrate content in the diet
from 39% or 355 g to 65% or 602 g · day–1 (4.6 and
7.9 g · kg–1 body mass) improved intermittent
endurance performance. Similarly, it has been
observed that performance during long-term
intermittent exercise consisting of 6-s work
periods separated by 30-s rest periods was
related to the initial muscle glycogen concentration (Balsom 1995).
The findings in the above mentioned studies
suggest that elevated muscle glycogen levels
prior to competition can increase the mean work
rate during a team sport match. In agreement
with this suggestion are findings in a study of
soccer players. It was observed that the use of
glycogen was more pronounced in the first than
in the second half of a game (Saltin 1973). Furthermore, the players with initially low glycogen
covered a shorter distance and sprinted significantly less, particularly in the second half, than
the players with normal muscle glycogen levels
prior to a match (Saltin 1973). It can be assumed
that the players would have been better prepared
for the second half if the muscle glycogen stores
had been higher prior to the match.
In may not only be towards the end of a match
that the level of muscle glycogen affects performance. In a study using 15 repeated 6-s sprints
separated by 30-s rest periods, it was found that
performance was significantly increased when
the subjects had elevated the muscle glycogen
stores prior to the exercise (Fig. 44.5). In agreement with this finding, it has been observed that
high muscle glycogen levels did not affect performance in single intense exercise periods, but
when exercise was repeated 1 h later, fatigue
578
sport-specific nutrition
Field running
Rest
Treadmill running
A
B
0
(a)
46
60
C
95
Time (min)
Exercise
period
1–7
3, 5
4
Blood
sample
Gas
collection
Speed (km.h–1)
25
18
15
12
8
6
0
0
1
(b)
2
3
Time (min)
4
5
Blood
sample
Gas
collection
Speed (km.h–1)
18
12
8
0
0
102
109
113
Time (min)
120
(c)
occurred at a later stage when the subjects started
with superior muscle glycogen concentrations
(Bangsbo et al. 1992a). It is worthwhile to note
that in both studies the muscle glycogen level
was still high at the point of fatigue where fatigue
was defined as an inability to maintain the
127
Fig. 44.4 Protocol of an
intermittent endurance test.
(a) The test consisted of 46 min of
intermittent field running
followed by 14 min of rest and
then by two parts of intermittent
treadmill running to exhaustion.
(b) The first part of the treadmill
running consisted of seven
identical 5-min intermittent
exercise periods. (c) The second
part of the treadmill running
shows where the treadmill speed
was alternated between 8 and 18
km · h–1 for 10 s (䊐) and 15 s ( ),
respectively. After 17 min, the
lower speed was elevated to
12 km · h–1, and the running was
continued until exhaustion.
Adapted from Bangsbo et al.
(1992b), with permission from the
International Journal of Sport
Medicine.
required power output. During intense intermittent exercise, both slow-twitch (ST) and fasttwitch (FT) fibres are involved (Essen 1978) and a
partial depletion of glycogen in some fibres, particular the FT fibres, may result in a reduction in
performance. These studies demonstrate that if
team sports
579
End pedalling frequency (rev.min–1)
140
*
*
130
*
*
14
15
120
0
1
2
3
4
5
6
7
8
9
No. of work periods
10
11
12
13
Fig. 44.5 Pedalling frequency during the last 2 s of 15 ¥ 6-s periods of intense cycling separated by 30-s rest periods
with a diet low (䊏) and high ( ) in carbohydrates in the days before the test. The subjects were supposed to
maintain a pedalling frequency of 140 rev · min–1. Note that after the high-carbohydrate diet the subjects were better
able to keep a high pedalling frequency. *, significant difference between high- and low-carbohydrate diet. Adapted
from Balsom (1995), with permission.
the muscle glycogen levels are not high prior to a
game, performance of repeated intense exercise
during the game may be impaired.
Diets of athletes in team sports
The above mentioned studies clearly show that
high glycogen levels are essential to optimize
performance during intense intermittent exercise. However, athletes in team sports may not
actually consume sufficient amounts of carbohydrate, as illustrated in a study of Swedish elite
soccer players. After a competitive match played
on a Sunday, the players were monitored until
the following Wednesday, when they played a
European Cup match. One light training session
was performed on the Tuesday. Immediately
after the match on Sunday, and on the following
2 days, muscle samples were taken from a
quadriceps muscle for determination of glycogen content (Fig. 44.6). After the match, the
muscle glycogen content was found to be
reduced to approximately 25% of the level before
the match. Twenty-four hours (Monday) and 48 h
(Tuesday) later, the glycogen stores had only
increased to 37% and 39% of the prematch level,
respectively. Muscle samples were not taken on
the Wednesday because of the European Cup
match, but it can be assumed that the glycogen
stores were less than 50% of the prematch levels.
Thus, the players started the match with only
about half of their normal muscle glycogen
stores, which most likely reduced their physical
performance potential.
The food intake of each player was analysed
during the same period (Sunday to Wednesday).
The average energy intake per day was 20.7 MJ
(4900 kcal), with a variation between players
from 10.5 to 26.8 MJ (2500–6400 kcal). By use of
the activity profile and body weight of each
player, it was calculated that most of the players
should have had an intake of at least 20 MJ
580
sport-specific nutrition
75
50
Pre European
Cup match
48 h
post-match
24 h
post-match
Post-match
25
Pre-match
Glycogen content (%)
100
Fig. 44.6 The muscle glycogen content of a quadriceps
muscle for players in a Swedish top-class soccer team,
before and just after a league match (Sunday). The
figure also gives muscle glycogen values 24 and 48 h
after the match, and an estimate of the level before a
European Cup match on the following Wednesday
(dashed bar). The values are expressed in relation to
the level before the league match (100%). Note that
muscle glycogen was only restored to about 50% of the
‘normal level’ before the European Cup match.
Adapted from Bangsbo (1994b), with permission from
HO + Storm.
(4800 kcal). Therefore, for some of the players the
total energy consumption was much lower than
required.
The quality of the diet must also be considered,
e.g. the proportion of protein, fat and carbohydrate. The players’ diet contained, on average,
14% protein of total energy intake (which lies
within the recommended range), 47% carbohydrate and 39% fat. If these percentages are compared with those recommended of at least 60%
carbohydrate and no more than 25% fat, it is
evident that the carbohydrate intake by the
players was too low on the days before the European Cup match. This factor, together with the
relatively low total energy consumption of some
players after the Sunday match, can explain the
low muscle glycogen stores found on the days
prior to the European Cup match. Thus, the diet
of the players was inadequate for optimal physical performance.
It is evident that many athletes in team sports
are not aware of the importance of consuming
large amounts of carbohydrates in the diet. It
may be possible to achieve major changes in
dietary habits just by giving the players appropriate information and advice.
In the study concerning the effect of a
carbohydrate-rich diet on intermittent exercise
performance, 60% of the soccer players’ diet was
controlled and within given guidelines they
could select the remaining 40% themselves.
Using this procedure, the average carbohydrate
intake was increased from about 45% in the
normal diet to 65% in the high-carbohydrate
diet. The foods that were consumed in the
carbohydrate-rich diet are found in most households. This means it is not necessary to drastically change dietary habits in order to obtain a
more appropriate diet.
Everyday diet
carbohydrates
It is clear that eating a carbohydrate-rich diet on
the days before a match is of importance for performance. To consume a significant amount of
carbohydrate in the everyday diet is also beneficial to meet the demands of training. Figure 44.7
illustrates how the muscle glycogen stores may
vary during a week of training for a player that
consumed either a high-carbohydrate diet or a
‘normal’ diet. During training, some of the glycogen is used, and between training sessions the
stores are slowly replenished. If the diet contains
large amounts of carbohydrate, it is possible to
restore glycogen throughout the week. This
may not be achieved if the diet is low in
carbohydrates.
An increase in glycogen storage is followed by
an enhanced binding of water (2.7 g water · g–1
glycogen). Thus, a high-carbohydrate diet is
likely to result in an increase in body weight,
which might adversely affect performance in the
early stage of the match. However, this effect is
probably small and the benefit of high muscleglycogen concentrations before a match will
probably outweigh the disadvantages of any
team sports
581
Glycogen level (%)
100
75
50
25
0
Activity:
Sun
Match
Mon
Tues
Training Training
Wed
Thurs
Training
Fri
Sat
Training
Sun
Match
Fig. 44.7 A hypothetical example of how muscle glycogen stores can vary during a week for a soccer player with a
high-carbohydrate (circles) and a ‘normal’ (squares) diet. There is a match on Sunday, a light training session on
Monday, an intensive training session on Tuesday and Thursday, and a light training session on Saturday. The filled
symbols indicate the values after the match and training. Note that the glycogen stores are replenished at a faster
rate with the high-carbohydrate diet, thus allowing for proper preparation for training and the subsequent match.
In contrast, consuming a ‘normal’ diet may result in reduced training efficiency and the glycogen stores may be
lowered before the match. Adapted from Bangsbo (1994b), with permission from HO + Storm.
increase in body weight. The maximal additional
muscle-glycogen synthesis when consuming
a high-carbohydrate diet as compared with a
normal diet should be 150 g, which corresponds
to a weight gain of less than 0.5 kg. Furthermore,
a more pronounced breakdown of glycogen will
enhance the release of water, which will reduce
the net loss of water.
protein
Protein is used primarily for maintaining and
building up tissues, such as muscles. The amount
of protein required in the diet is a topic frequently discussed, particularly with respect to
those sports where muscle strength is important
or where muscle injuries often occur. Most team
sports can be included in both of these categories.
However, in most cases the athletes take in sufficient amount of proteins (see Chapter 10). For
example, the daily intake of protein by Swedish
and Danish soccer players was 2–3 g · kg–1 body
weight, which is above the recommended daily
intake for athletes of 1–2 g · kg–1 (Jacobs et al. 1982;
Bangsbo et al. 1992b). In general, supplementing
protein intake by tablets or protein powders is
unnecessary for athletes in team sports, even
during an intensive strength-training period.
fat
Fat exists in two forms — saturated fat and unsaturated fat. The saturated fats are solid at room
temperature (butter, margarine and fat in meat)
while unsaturated fats are liquid or soft at room
temperature (vegetable oil, vegetable margarine
and fat in fish). An adequate intake of unsaturated fats is essential for the body, and, in contrast to saturated fats, unsaturated fats may aid
in lowering the amount of cholesterol in the
blood, thereby reducing the risk of heart disease.
Therefore, it is important that saturated fats are
replaced with unsaturated fats where possible.
The total content of fat in the average diet for an
athlete is often too high and a general lowering of
fat intake is advisable.
582
sport-specific nutrition
minerals and vitamins
Food and drink supplies the body with fluids,
energy-producing substrates, and other important components, such as salt, minerals, and vitamins. In a well-balanced diet, most nutrients are
supplied in sufficient amounts. However, there
can be some exceptions.
Iron is an important element in haemoglobin,
which binds to the red blood cells and aids in the
transport of oxygen throughout the body. Therefore, an adequate iron intake is essential for athletes and especially for female athletes, who lose
blood and, thus, haemoglobin during menstruation (see Chapter 24). The recommended daily
intake of iron for a player is approximately
20 mg, which should be ingested via solid foods
rather than in tablet form, as iron found in solid
foods is more effectively absorbed from the intestine to the blood. Animal organs (liver, heart and
kidneys), dried fruits, bread, nuts, strawberries
and legumes are foods with a high content of
iron. It is advisable to increase iron intake in
periods when players are expected to increase
their red blood cell production, e.g. during the
preseason or when training at a high altitude.
A question commonly asked is whether or not
players should supplement their diet with vitamins. In general, vitamin supplementation is
not necessary, but there are conditions where it
might be beneficial. For example, it is advisable
to enhance vitamin E intake when training at
high altitudes, and to use vitamin C and multiple
B-vitamin supplements in hot climates (see
Chapters 20 and 26).
creatine
In team sports, the rate of muscle PCr utilization
is high during periods of match play and in the
following recovery periods PCr is resynthesized
(see above). This leads to the question whether
an athlete in team sports can benefit from ingestion of creatine in a period before a match, as it
has been shown that intake of creatine increases
the PCr and particularly creatine levels in
muscles (Harris et al. 1992). For example, it was
found that five subjects increased their total
muscle creatine level (PCr and creatine) by 25%
after a creatine intake of 20 g · day–1 for 5 days
(Greenhaff et al. 1994). The effect of intake of creatine is discussed in detail in Chapter 27 and the
discussion here will focus on issues relevant to
the team games players.
An elevated level of creatine and PCr may
affect PCr resynthesis after exercise (Greenhaff et
al. 1994), which may have an impact on the
ability to perform intermittent exercise. In one
study, subjects performed 10 6-s high-intensity
exercise bouts on a cycle-ergometer separated by
24 s of rest, after they had ingested either creatine
(20 g · day–1) or placebo for a week (Balsom et al.
1993a). The group which ingested creatine had a
lower reduction in performance as the test progressed than the placebo group. On the other
hand, as one would expect, creatine ingestion
appears to have no effect on prolonged (> 10 min)
continuous exercise performance (Balsom et al.
1993b).
Although creatine ingestion increases muscle
PCr and creatine concentration, it is doubtful that
athletes in team sports, except probably for vegetarians, will benefit from creatine supplementation, since creatine ingestion also causes an
increase in body mass. It is still unclear what
causes this increase, but it is most likely due to an
increased accumulation of water. Nevertheless, a
gain in body weight has a negative influence in
sports in which the athletes have to move their
body mass against gravity. For example, no difference in performance during intense intermittent running (Yo-Yo intermittent recovery test)
was observed when a group of subjects performed the test after 7 days of creatine intake
(20 g · day–1) compared with a test under control
conditions. Furthermore, it is unclear how
ingesting creatine for a period influences the
body’s own production of creatine and the
enzymes that are related to creatine/PCr synthesis and breakdown. It may be that an athlete,
through regular intake of creatine, reduces his
ability to produce PCr and creatine, which may
result in a reduction in the PCr and creatine
levels when the athlete no longer is ingesting
team sports
583
creatine. In addition, very little is known about
any possible side-effect of a frequent intake of
creatine. Regular high concentrations of creatine
in the blood may, on a long-term basis, have
negative effects on the kidney, which is the organ
that has to eliminate the excess creatine. One
should also consider that ingestion of creatine
can be considered as doping, even though it is
not on the IOC doping list. It may be argued that
creatine is a natural compound and that it is contained in the food. However, it is almost impossible to get doses of creatine corresponding to
those used in the experiments which showed
enhanced performance, as the content of creatine
in 1 kg of raw meat is around 5 g.
utilization and a reduction in exercise time to
exhaustion (Costill et al. 1977). However, not
all studies have shown a detrimental effect of
ingesting carbohydrate before exercise, and
some studies have shown improved performance after carbohydrate ingestion in the last
hour prior to strenuous exercise (Gleeson et al.
1986). The differences seem to be closely related
to the glucose and insulin responses. When exercising with a high insulin concentration, there is
an abnormally large loss of glucose from the
blood, resulting in a low blood glucose concentration. Consequently, the muscles and the brain
gradually become starved of glucose, which
eventually leads to fatigue.
Pretraining and precompetition meal
Food intake after exercise
On the day of a match, the intake of fat and
protein (especially derived from meat) should be
restricted. The pretraining or prematch meal
should be ingested 3–4 h prior to competition
or training. If too much food is ingested after
this time, there still may be undigested food in
the stomach and intestine when the training or
match begins. The meal should mainly consist of
a sufficient amount of carbohydrate. It has been
demonstrated that ingestion of 312 g of carbohydrate 4 h prior to strenuous continuous exercise
resulted in a 15% improvement in exercise performance, but no improvement was observed
when either 45 or 156 g of carbohydrate was
ingested (Sherman et al. 1989). A snack high in
carbohydrate, e.g. bread with jam, may be eaten
about 1.5 h before the match. However, these
time references are only guidelines. There are
great individual differences in the ability to
digest food. It is a good idea for players to experiment with a variety of different foods at different
times before training sessions.
An improvement in exercise performance
has been observed if carbohydrate was ingested
immediately before exercise (Neufer et al. 1987).
On the other hand, glucose ingestion 30–60 min
prior to severe exercise has been shown to
produce a rapid fall in blood glucose with the
onset of exercise, an increase in muscle glycogen
Physical activity is a powerful stimulus to glycogen resynthesis, as was elegantly shown in a
study where a glycogen-depleted leg attained
muscle glycogen levels twice as high as the
resting control leg during a 3-day period
(Bergström & Hultman 1966). In addition, it
seems that the muscles are particularly sensitive
to glucose uptake and glycogen resynthesis in
the period immediately after exercise (Ploug et al.
1987). It was found that the rate of glycogen
resynthesis during the first 2 h after carbohydrate
intake was faster if carbohydrate was ingested
immediately following an exercise bout, rather
than delaying the intake by 2 h (Ivy et al. 1988).
Thus, to secure a rapid resynthesis of glycogen,
an athlete should take in carbohydrates immediately after training and a match. For specific
recommendations about amount and type of carbohydrate, see Chapter 7.
An inverse relationship between the rate of
glycogen rebuilding and the muscle-glycogen
concentration after prolonged continuous exercise or soccer match-play has been demonstrated
(Piehl et al. 1974; Jacobs et al. 1982). Therefore, in
team sports the players should be able to replenish the muscle glycogen stores within 24 h after
a match, irrespective of the magnitude of the
decrease of carbohydrates during the game.
However, other factors have been shown to influ-
584
sport-specific nutrition
ence the rate of glycogen synthesis. Glycogen
restoration is impaired after eccentric exercise
and after exercise causing muscle damage (Blom
et al. 1987; Widrick et al. 1992). In most team
sports the players are often performing some
eccentric exercise and muscle damage can occur
due to physical contact. It has been demonstrated
that an increased ingestion of carbohydrate
can partially overcome the effect of the muscle
damage on glycogen resynthesis (Bak & Peterson
1990). Thus, also in this respect the players can
benefit from a high carbohydrate intake following match-play and training.
Fluid intake in team sports
In many team sports, the loss of body water,
mainly due to the secretion of sweat, can be large
during competition. For example, under normal
weather conditions the decrease in body fluid
during a soccer match is approximately 2 l, and
under extreme conditions the reduction in body
water can be higher, e.g. in a World Cup soccer
match in Mexico, one Danish player lost about
4.5 l of fluid. Such changes in body fluid can
influence performance negatively during matchplay (Saltin 1964). Thus, it is important for the
players to take in fluid during a game and also
during a training session to maintain the efficiency of the training. The question is what and
how much to drink before, during and after a
training session or a game.
Before a training session or match
It is important that the players are not dehydrated before a match. The players should begin
the process of ‘topping-up’ with fluid on the day
before a match. For example, an additional litre
of juice can be drunk on the evening before a
match, which will also provide an extra supply of
sugar.
On the match day, the players should have
plenty to drink and be encouraged to drink even
when they are not feeling thirsty. The content of
sugar should be less than 10%. During the last
hour before the match, the players should not
have more than 300 ml (a large cup) of a liquid
with a sugar concentration less than 5% every
15 min.
The intake of coffee should be limited, as coffee
contains caffeine, which has a diuretic effect and
causes the body to lose a larger amount of water
than is absorbed from the coffee.
During a training session or match
Besides reducing the net loss of body water, the
intake of fluid can supply the body with carbohydrates. As low muscle glycogen concentrations
in some team sports might limit performance at
the end of a match, intake of carbohydrate solutions during a match is useful.
Questions remain concerning the optimum
composition of the drink, particularly with
respect to its concentration, form of carbohydrates, electrolyte content, osmolality, pH,
volume and temperature. These considerations
depend, among other things, on the temperature
and humidity of the environment, which should
determine the ratio between the need for fluid
and need for carbohydrates. In a cold environment, there is little need for water, and a drink
with a sugar concentration up to 10% can be
used, whereas in a hot environment the carbohydrate content should be much less. Before using
drinks with high sugar concentrations in a
match, however, the players should have tried
these drinks during training to ensure that
stomach upset does not occur. There are large
individual differences in the ability to tolerate
drinks and to empty fluid from the stomach.
While some players are unaffected by large
amounts of fluid in the stomach, others find it
difficult to tolerate even small quantities of fluid.
The players will benefit by experimenting with
different drinks and drinking habits during
training. For further discussion of the compositions of the fluid, see Chapters 17 and 39.
During a match, small amounts of fluid should
be drunk frequently. It is optimal to drink
between 100 and 300 ml with a 2–5% sugar con-
team sports
centration every 10–15 min. In a soccer match,
this will give a total fluid intake of between 1 and
2 l, plus 30–50 g of sugar during the match. This is
sufficient to replace a significant amount of the
water lost through sweat, and to cover some of
the demand for sugar. Although fluid intake
during a match is important, it should not
interfere with the game. The players should
only drink when there is a natural pause in the
game as the drinking may disturb the playing
rhythm. In some team sports, such as basketball
and ice-hockey, the players can drink during
time-outs or when they are on the bench,
whereas in other sports, such as soccer, it is more
difficult. In the latter case, it is convenient to
place small bottles of fluid at different positions
around the field in order to avoid long runs to the
team bench.
585
and on the day of the match — more than just to
quench thirst.
• Drink frequently just before and during a
match as well as at half-time, but only small
amounts at a time — not more than 300 ml of fluid
every 15 min.
• Drinks consumed just before and during a
match should have a sugar concentration lower
than 5% and a temperature between 5 and 10 °C.
• Drink a lot after a match — even several hours
afterwards.
• Use the colour of the urine as an indication of
the need for fluid — the yellower the urine, the
greater the need for fluid intake.
• Experiment with drinking habits during training so that any difficulties in absorbing fluid
during exercise can be overcome.
Conclusion
After a training session or match
The players should drink plenty of fluid after a
match and training. Several studies have demonstrated that restoration of fluid balance is a slow
process and that it is not sufficient merely to
increase fluid intake immediately after a match
(see Chapter 19). It is not unusual for players
to be partially dehydrated on the day after a
match. The body can only partially regulate
water balance through the sensation of thirst, as
thirst is quenched before a sufficient amount of
fluid has been drunk. Thus, in order to maintain
fluid balance, more fluid has to be drunk than
just satisfies the sensation of thirst.
The colour of urine is a good indicator of the
fluid balance and the need for water. If the body
is dehydrated, the amount of water in the urine
is reduced and the colour becomes a stronger
yellow.
Recommendations
The following recommendations regarding fluid
intake may be helpful for an athlete in team
sports:
• Drink plenty of fluid the day before a match
In most team sports, the players perform highintensity intermittent exercise, at times for a
long duration. The intense exercise periods
require a high rate of energy turnover and the
total energy cost of a game can be high. Muscle
glycogen appears to the most important substrate in team sports, and performance may be
limited due to a partial depletion of the muscle
glycogen stores.
Athletes that are taking part in team sports
should have a balanced diet that contains large
amounts of carbohydrate to allow for a high
training efficiency and for optimal preparation
for matches. Therefore, it is important for the
players to be conscious of the nutritive value of
the food that they consume. The highest potential for storing glycogen in the muscles is immediately after exercise. It is therefore advisable to
consume carbohydrate, either in solid or liquid
form, shortly after a match or training session.
This is particularly important if the players are
training twice on the same day. On the day of
competition, the last meal should be ingested 3–
4 h before the start, and it should mainly consist
of carbohydrates that can be rapidly absorbed.
During the last hour before a match, solid food or
586
sport-specific nutrition
liquid with a high carbohydrate content may be
avoided.
To limit the extent of dehydration and to
provide the body with carbohydrate during
match-play, the players should take in fluid with
a low carbohydrate content both before and
during a match. Also, fluid ingestion should be
high after a match.
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